1. Field of the Invention
The claimed invention relates to methods and apparatus to measure position changes, i.e., displacements and rotations, of a sensed object in space, in six degrees of freedom (six-DOF).
2. Optical Sensor Applications
The assembly of mechanical items often requires that relatively large parts be fit together with very small dimensional tolerances. Such tasks pose a challenge for automation because the scales involved in the process typically span several orders of magnitude. Generally, the larger and more massive the parts to be assembled, the more substantial the assembly machine required to perform the task. As the assembly machine increases in size, however, the accuracy of open-loop control methods generally decreases.
One can significantly improve the accuracy of the assembly process by using closed-loop control techniques, but only if real-time sensory information on the relative location of parts to be assembled is available. Additionally, the accuracy of the closed-loop assembly process is limited by the accuracy of the sensed information. Hence, operations requiring high accuracy placement of parts must use high resolution sensors in closed-loop control systems. In some cases, the sensors must be multidimensional, detecting both translation and rotation of parts.